In the early days of fluidized bed and pans coating processes, organic solvents were
used in the preparation of coating solutions. They allowed fast coating at relatively
low fluidization gas rates and temperatures, but their use has declined because of the
stringent regulations on industrial hygiene, the working environments and safety
measures required during their use. There has been an increasing use of aqueous
solutions to replace the organic solvents, and these require higher fluidizing air
capacities and heating systems. The concentration of the coating solution is limited to
the range where the solution remains sprayable.